Got it.  Well, it may be the case I need to start using it with some of my music.  I just did not want to start curtailing what the system is capable of offering.  Since the issue is not dramatic, I could still endure it during the break-in, even without the treble control, although I will be trying it later on.

Thanks for the tip.

Worth playing with during break in as well. What's the harm in curtailing some frequencies that are too much either due to break in, component quality, or room issues? Get the enjoyment you paid for! You can always turn the controls off once a day and do a "reality check."

I wouldn't jump to the conclusion that your DAC or cables are causing the issue just yet.  They may be at fault (I highly doubt it, but maybe).  First address the more fundamental room/speaker part of the equasion before fixing something thay probably doesn't need fixing.  An improved DAC and cables may make a difference, but orienting the speakers and treating the room to address the wide treble pattern the speakers throw will certainly make a difference.  

Read the setup and considerations portions of this review which discuss this in detail:
http://www.stereomojo.com/DECWARE%20DM945%20MINI%20SPEAKER%20REVIEW.htm/DECWARED...

The author reports good results using a cross-fire type orientation.  Perhaps give that a try.

And Lon's right.  Don't hesitate to adjust the treble knob, it won't adversely effect sonics.

I think this could very well be break in, but also the amp and speakers are giving you so much signal, so much detail, and some of it is less refined right now before tweeter and amp components are fully settled in.

Definitely experiment with speaker placement, and consider room treatment, adjust the treble cut, and also try the system without the isolation transformers. I came to the conclusion that those I had were adding unwanted noise that showed up as a bit of raggidiness.

Checked the link.  I had forgotten all about it, as I had read it long time ago.  Their points concerning my issues are consistent with the re-positioning and room conditioning tasks I'm facing.  

Let me clarify that I love these speakers and the only caveat I'm noticing (as described) may well be something minor, the solution of which is probably well within my reach.  

So far, I have stuck with the equilateral triangle concept in my toeing-in approach.  I guess I have all sorts of other angle possibilities open for trial and error, and I will probably find the best in my particular case.  The only real constraint is the distance from the speakers' back wall. This is limited to some 18", albeit at an angle, which may equate to some additional distance.

Problem solved!  Believe it or not, this morning I placed the speakers straightforward facing, no toe-in, and the higher register issue disappeared.  No more congestion, just plain wonderful sounds.  It may have been incidental to the break-in curve stage, but in this position I really love these speakers.

Contrary to what the Stereo Mojo review suggested (which seemed counter-intuitive to me anyway), it seems in my case there was some addition of high frequencies stemming from the toe-in placement.  I guess those waves overlapped or something similar, at those angles.  In any event, the dispersion now apparently has more room to propagate  without any overlapping, and those high frequency notes become pristine when listening to really well recorded material.

I can't explain the reasons, but this morning I listened for about 6 hours in a row with that placement and not once I felt the constipation issue again ... Now it seems as if the system is almost broken-in (which it's not, but to me it sounds delicious already).

The only doubt I have is if I may be missing some sound patterns given the non directionality of the speakers to the sweetspot (as in the equilateral triangle principle), but I would be nick-picking here.  So long as it sounds the way it does now, I'm happy, as I don't seem to be missing any details.

The more I dwelve into audiodome, the more puzzled and surprised I become.  Go figure!

Worth it indeed.  It's the best audio decision I could've made, thanks to this forum's suggestions and support, and a wise choice from Steve.  I'm enjoying it very much.  It's still too early, but the progress from friday has been amazing.  Now, I think I can finally put my arms around it in terms of my expectations from this gear, as I can hear its potential first hand.

Re the overlapping of higher frequencies from the tweeters, IMHO either they are oriented to cancel each other (i.e., in front of the presumed sweetspot), or they are provided enough space to propagate without too much overlapping (forward facing placement, as in my case).  From these alternatives, if the distance between both speakers is large enough, I would favor the latter.  But, I may be totally wrong, as it could also depend on uneven reflecting surfaces nearby and so on.

The point is, I'm having a ball with it.  Have a nice listening yourself.